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EN
Spin-dependent transport properties of a single-electron transistor have been analysed, whose two external electrodes and the central part (island) are ferromagnetic. Based on the real-time diagrammatic technique, all transport contributions have been calculated up to the first order in the coupling strength between the island and the leads – this comprises a sequential tunnelling. Relevant occupation probabilities of different charge states are determined from the generalized master equation in the Liouville space. Assuming that spin relaxation processes on the island are sufficiently fast to neglect spin accumulation, we analyze electric current flowing through the system in the parallel and antiparallel magnetic configurations, as well as the resulting tunnel magnetoresistance. We show that transport characteristics of ferromagnetic single-electron transistors exhibit a strong dependence on the magnetic configuration of the system. Furthermore, we also demonstrate that the bias dependence of both the differential conductance and tunnel magnetoresistance displays an oscillatory-like behaviour resulting from single-electron charging effects.
EN
Theoretical analysis of the spin-transfer torque acting on the magnetic moment of the central electrode (island) in a single-electron ferromagnetic transistor has been performed for the spin relaxation time in the island ranging from fast to slow spin relaxation limits. The magnetic configuration of the system can be generally arbitrary. Spin accumulation on the island, due to the spin asymmetry of tunnelling processes, is taken into account. Electric current flowing through the device is calculated in the regime of sequential transport, and the master equation is used to calculate probabilities of different charge and spin states in the island. The torque acting on the central electrode is then calculated from the spin current absorbed by magnetic moment of the island.
EN
Electronic transport in a ferromagnetic single-electron transistor is analysed theoretically in the sequential tunnelling regime. One of the external electrodes and the central part (island) of the device are assumed to be ferromagnetic, with the corresponding magnetizations being non-collinear. The analysis is based on the master equation method, and the respective transition rates are determined from the Fermi golden rule. It is shown that the electric current and corresponding tunnel magnetoresistance (TMR) strongly depend on the angle between the magnetizations. For an arbitrary magnetic configuration, TMR is modulated by charging effects, which give rise to characteristic dips (cusps) at the bias voltages corresponding to the Coulomb steps in the current-voltage characteristics.
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